Improvement in pneumatic signals for railway-crossings



W. E. PR'ALL.

ENEUMATIc-SIGNALS FOR RAILWAY-CROSSINGS.

Patente Jan. 18

N. PETERS. PHOTO-LITHOGRAPHER, WASHlNGTOYI. D C.

WILLIAM E. PEALL, OE WASHINGTON, D. o., ASSIGNOE TO PEALL RAILWAY SIGNAL AND TELEGEAPH COMPANY, OE NEW YORK, N. Y.

IMPROVEMENT IN PNEuMAT-Ic SIGNALS FOR RAILWAY-CROSSINGS Specification forming part of Letters Patent No. 172,49 l, dated January 18, 1876i application filed Y September 7, 1874.

CASE H.

To all whom it may concern:v

Be it known that I, WILLIAM E. PRALL, of

` Washington city, in the District oi' Columbia,

have invented an Improvement in Pneumatic Signals for Railway-Crossings, oi' which the following is a specification:

My invention relates to an improved apparatus for signaling, by means of compressed air, the approach of a train, simultaneously, at a number of crossings, either by sounding an alarm, displaying a simple cautionary signal, or closing a gate at each crossing of a street or road.

Figure l of the accompanying drawing illustrates the simplest form of my invention; and Fig. 2 illustrates a modification thereof.

A is a main pipe extending the entire distance ofthe section of road where the gates or signals are to be employed, and which is to be kept constantly charged with air under compression. B is a Signal-pipe extending parallel to the main pipe and roadway, vso far `asit is desired, to effect a simultaneous display of signals, or closing of gates. C C are improved gates, consisting oi' a fringe of long cords, d d, depending from a movable bar suspended from pulleys operated by means ot' an air-piston and cylinder, M, so as to raise and lower the gate, all as is fully described in Letters Patent heretofore granted to me for the same. These gates are to be placed at theintersection ofthe railroad with the streets or roads in towns or cities, to close the way whenever a train is about to pass. The air-piston cylinders M M of the several gates are connected by branch pipes F F with the one signal-pipeB, so that whenever the compressed air is admitted to said pipe all of the gates will be simultaneously shut down by the movement of their said pistons. G G are simple check valves placed in the signalpipe in advance of each gate, so as to permit the air to pass freely through the pipe by and beyond each gate in theone direction, as indicated by the arrows; but to prevent a return or reilow of the air which has thus filled the several separate Sec tions formed and separated by said valves. H is a cock or valve placed at the intersection Vof the main and signal pipes to open and close the connection between the two. This cock may be operated automatically by a passing train, or otherwise by a switchman or other attendant upon the approach ofthe train. K K are automatic exhaiistvalves or commutators, which may be constructed substantially as described in Letters Patentheretofore granted to me, and which, being operated by the passing train through the intervention of levers thereon, to be struck by an attachment in the locomotive or on one of the cars, will throw open an exhaust-vent, and allow the air in the piston-cylinder and pipe to exhaust and thus permit the gate to rise and open. In these commutators the pressure-piston, 'by

which the exhaust-valve is automatically lield" open, may be supplied with air from the supply-pipe B, instead of from the air-main A. The check-valves G serve to prevent the exhaust of air from any one section through the exhaust-valve of the preceding section, when the latter is thrown open. Any desired number of gates may be closed simultaneously and be thereafter automatically opened, one at a time, as the train passes.

I contemplate the` substitution ot' any suitable form or character ot' signal to be operated by means of compressed air delivered from the pipe B instead of the gates C, and the same may be displayed and withdrawn, or sounded and silenced, in the like manner.

In the series of gates or guard-signals ar ranged as illustrated in Fig. 2 of the drawings, air is admitted from the main pipe A to the signal-pipe B by means of a three-Way exhaustcock, K1, to be operated by a switchman, who, so soon as the the train has passed him, will, by closing the cock, open an exhaust for the signal-pipe, and thus reopen the gate or gates connected With the section nearest him, the length of this section being determined by the position of the check-valve G', which serves to prevent an escape oi' air through said exhaust from the portion of pipe beyond it. The section of pipe beyond the check-valve is in turn relieved from pressure, and the gates combined therewith are left free to open, by

FFCE.

the operation of an exhaust-commutator at the extreme end thereof to be actuated by the passing train. g' y v In this arrangement of signals the pipesF, communicating with the air-pistons operating the gates or signals, are connected directly with the air-main A, instead of with the signal-pipe B but these pipes are each controlled by a coel'; or val-ve, P, opened and closed by means of a second piston or diaphragm, R, operated by the admission and exhaust of air to and from the said signal-pipe B. The movement of these several secondary pistons or diaphragms R R may be so adjusted as that each in succession, from the first to the last, shall move more slowly than that preceding it, so that the instantaneous admission of air to the 'signal-pipe B shall, instead of producing a simultaneous movement of all the gates or signals, as first above described, cause them, by means of a suitable adjustment of the'pistons, to'move in 'succession one after the other in due order and proper time before the advancing train. Diaphragms may, in all eases, be substituted for pistons in the construction of the above-described apparatus.

I claim as my invention- An air-signal pipe, B, provided with one or more automatic check-valves, G G', and cornbined with one or more exhaust-valves, K K1, to operate successively, substantially as and for the purpose herein set forth.

' W. E. PRALL.

Witnesses:

DAVID A. BURR, WM. E. KNoWLEs. 

